Stone to kilograms Converter

How many kilograms are in a stone?

One stone is 6.350293 kilograms. The full conversion is kilograms = stone × 6.35029318, and going the other way you divide instead of multiply.

A few anchor values worth memorising: 6.350293 kg to the stone, 63.502932 kg to ten, and 635.029318 kg to a hundred. The calculator above handles the rest, including the awkward decimals.

The reference table under the converter lists the values people look up most often, so for a common figure you can read the answer off directly rather than typing anything.

Worked examples

Three worked examples, each multiplying by 6.35029318:

2.5 st × 6.350293 = 15.8757 kg. 25 st × 6.350293 = 158.7573 kg. 250 st × 6.350293 = 1,587.5733 kg.

To reverse any of them, divide instead of multiplying — or use the swap button above, which does the same thing without the arithmetic. Reversing a converted value should return you to exactly what you started with; if it does not, something has been rounded too early.

Doing this conversion in your head

The exact factor is 6.35029318, which nobody multiplies by in their head. It is very close to 70/11, so multiplying by 70 and dividing by 11 lands within 0.21% of the correct answer — accurate enough for anything short of engineering work.

Since the factor is greater than one, the number always gets bigger: a stone is smaller than a kilogram, so any quantity converts to more of them. If your answer came out smaller, you have divided when you should have multiplied.

That sanity check catches the majority of real conversion errors. Before trusting any converted figure, ask whether the direction of change makes sense — it takes a second and it is the single most effective safeguard there is.

When you need to convert stone to kilograms

Whether you need three decimal places or a rough sense of scale depends entirely on why you are converting, so it is worth being clear about that first.

On the source side, stone is used for body weight in Britain and Ireland and essentially nowhere else. On the target side, kilograms are body weight, luggage allowances, grocery pricing and shipping quotes. The conversion is essentially a translation between those two worlds — most often because a figure produced in one context has to be understood, submitted or acted on in the other.

Where the converted figure will be cut, dosed, billed or filed, round once at the end rather than at each step. For a rough sense of scale, round freely.

None of this leaves your browser. The conversion is a few lines of arithmetic, so there is no server involved and nothing to store.

What a stone and a kilogram actually are

The stone (st). Fourteen pounds; still the default for body weight in Britain and Ireland.

The kilogram (kg). The SI base unit, redefined in 2019 in terms of the Planck constant rather than a metal cylinder in Paris.

Because both measure mass and their definitions are set by standards bodies, the factor between them never changes. It is not an approximation that improves with better instruments; it is a definition.

Common mistakes when converting stone to kilograms

Stones are only used for body weight, and only in Britain and Ireland. A weight given as "11 stone 4" means 11 × 14 + 4 = 158 pounds, not 11.4 stone — the second number is pounds, not a decimal fraction. Feeding "11.4" into a converter gives you the wrong answer by about three pounds.

For a batch of figures, set the units once and work down the list rather than converting via a third unit — each intermediate step introduces its own rounding.